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Blow-Out Port

I would like to have a drain valve (winterization blowout port) installed on the outside (there is already a drain valve and shut-off ball valve in the basement) so that I would not need to be home for them to blowout the sprinkler system.

Do I have the drain valve installed outside <b>before or after</b> the PVB (backflow preventer)??? Which way is right, I've seen it done both ways? Is this drain value required for winterization? Is this a DIY project, will an irrigation company install this, or will I need to get a plumber?

Depending on your location, you may not want to add a thing. The original standard configuration would have a drain hose bib on the low point of the plumbing, just after it exits the house, and upstream of the PVB. Nowadays, this faucet could be frowned upon, as a possible cross-connection, where the codes are making the assumption that some idiot will hook up a hose and connect it to something nasty. One way around this is to use a simple PVC plug in place of a boiler drain faucet. Remove plug, connect air, winterize, replace plug.

It is more than likely that local service companies already have any adapters they need to connect their air to a PVB testcock, which means the indoor drain doesn't have to be utilized for winterizing.

Downstream installation has the advantage of not presenting the possible cross-connection that upstream installation does, but we always appreciated the convenience of having a low-point drain valve that was open all winter, so water leaking past the sprinkler system shut-off valve had a means to safely drip away, and prevent freeze damage.

The outdoor low-point drain would have the advantage of not dripping water into a basement, when left open all winter. Modern installs don't really have a good way to deal with a leaking system-shutoff valve, if it's passing any quantity of water.

Yes, there is a low point drain value already in the basement. Last year he needed to access this drain while I was home to connect this hose. By installing one on the outside, will a contractor be able to accomplish the same task? How is it normally done in the Northeast?